Here's a fascinating notion: that sultry Hollywood sex goddess Hedy Lamarr invented radio technology employed by every mobile phone in use today.
The tech in question is the notion of spread-spectrum frequency hopping, a concept devised by Lamarr during World War II after learning German U-Boats had sunk a cruise ship and …

COMMENTS

Thought radio waves didn't penetrate water well at all? Hence all torpedoes being wire guided and subs having to send up screechy cables at opportune moments in the plot? So would these have had to have stayed very close to the surface?

@bolccg

Targets

Hmm, take you point about the article saying she intended to use it to attack "warships" but in the same breath (maybe the previous breath) it says the intention was to sink subs (and she started thinking about it due to a sub attack). Then again most subs in WW2 spent their time almost exclusively on the surface, I believe so I guess it works either way. Doesn't give you much time to steer onto target though, before they dive?

Guess it would've been interesting if the tech had existed to realise it to see how it worked out in practice.

Wow, that's incredible!

It's hard to believe a beautiful actress of the 1930's/40's was capable of such technological thinking that was ahead of her time given the stereotypical role a woman was expected to lead back in those days. Kudos to her for pursuing her passion and imagination.

Imagine what other inventions woman could have contributed if it wasn't for society's expectations for women to do traditional women's things. Or was Hedy a rare exception? Who knows. Excellent story.

I for one would welcome more equality and attractive female colleagues in my technical field of work. (Who can also sing, play the piano, act out a Princess Leia scene and bake the occassional cake)

That's Hopper

CDMA does not use Fast Hopping

CDMA, WiFi, and other similar spread-spectrum technologies don't use frequency hopping. They employ pseudorandom direct sequence spreading to smear their bits out over a much wider band. Not sure what is left using fast frequency hopping, bluetooth, and maybe the first couple spins of early 802.11 used it but the later ones surely don't.

I suspect that frequency hopping was easier to conceptualize and came first, then followed by the mathematically challenging direct sequence methods.

I only know of bluetooth that uses frequency hopping spread-spectrum, and I don't think it's really a solution for cellular tech.

Direct sequence CDMA is used much more, (ie WCDMA), which is also why 3G battery life is much less than 2G FD/TD multiplexing. Because everyone transmits simultaneously, the receiving tower needs all the incoming signals to be of equal strength, such that closer terminals don't drown out terminals further away. Leads to lots of fiddling with transmission power at the handset, hence reduced battery life.

From what I know, direct sequence CDMA also has it's origins in showbiz, although British, I think. Apparently Churchill and FDR used to chat over lines encrypted by playing a synchronised record over the voice - an inverted signal on the other side cancelled out the added LP, yielding clear speech to the listener, but no-one else.

Disclaimer:

I haven't done any work in this since final year elec eng, but I did get my old Bernard Sklar Digital Communications textbook out as a refresher. If there's any clarification on the invention of direct sequence, I'd be keen to follow any links provided.

Indeed. Most radios use Direct Sequence Spread Spectrum, not frequency hopping (though I worked on a series radios that used both, the Nomadio Sensor and React R/C controllers). DSSS takes a bit or a few bits, runs that though a "spreading code", and produces a large number of parallel, low bandwidth channels.

The big advantage of DSSS is protocol gain... on the receiving side of things, each of those narrow channels adds up, so you can see a pretty nice gain, 6, 12, 24dB depending on the specifics, just based on the DSSS protocol in use. Another advantage of the DSSS protocol is that your specific pseudo-random spreading code sequence makes local interference from other radios less interfering.

Frequency hopping has a different set of advantages. In the case of my R/C controller, each controller ran on one 1MHz channel out of a possible 80 in the 2.4GHz ISM band (same as Wi-Fi and most microwave ovens). But there's always the possibility of interference with other radio sources. If you have fixed channels, you can technically fit more radios at once, but some will get stuck in the noisy channel, others get the clean channel. With frequency hopping, everyone shares the same set of channels (we hopped at 100Hz.. not Bluetooth rates, but fast enough that this really did make a difference). We were the only R/C company at the time to use FHSS.